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American Airlines is adding an additional locking device on seats in 48 of its Boeing 757s to prevent the seats from becoming loose. (Published Friday, Oct. 5, 2012)

American Airlines said Thursday that it is taking additional measures to prevent rows of seats from becoming dislodged on 48 of its Boeing 757s.

In the last week, seats came loose on three flights involving Boeing 757s that were recently refurbished inside, including having seats removed and reinstalled. Two of the flights were forced to make emergency landings.

American said it was taking "additional preventative steps to enhance the locking mechanism features used to secure the seats to the aircraft floor" after further analysis by the airline's engineering team. Crews will add an additional locking device on the seat to make sure it doesn't move.

The airline said it would reinspect the 48 aircraft in concert with the Federal Aviation Administration when the aircraft are out of service.

"The work is expected to be completed after the 48 affected aircraft land at their next destination," the airline said.

American said the 48 planes are not being grounded, although some flights may be delayed or canceled to complete the work.

"We apologize to our customers for any inconvenience this may cause with their travel plans," the airline said. "The safety of our customers and people as well as the reliability of our fleet, is always of utmost priority to American."

American later said it would cancel 44 flights on Friday to fix the problem.

David Campbell, AA vice president of safety, security and environmental, said he expects some of the 757s will be back in the air by Friday. The rest should be back in service by Saturday.

American said the system used to attach the legs of each row of seats to the aircraft floor was the cause of the problem.

"American has instructed mechanics to pay particular attention to the seat lock plunger mechanism that secures the seat to the aircraft floor," AA said in a statement. "Mechanics have begun taking steps necessary to ensure that no seat can become dislodged from its track."

Campbell said gunk on the floor from normal passenger use is part of the problem.

"And over time, you get normal wear and tear and, as you get things like coffee and spilled Cokes, sodas and things down in the seat track, for these particular two, we believe that it built up and didn't allow the pin to reset or the locking pin to reset and hold the plunging mechanism in place," he said.

"The FAA is aware of American's decision to conduct further inspections on certain Boeing 757s and concurs with this step," FAA spokesman Lynn Lunsford said in a statement. "Our safety investigation continues, and we'll take additional action as appropriate."